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Cooter

Truck Auxiliary Transmission

7 posts in this topic

In my search for a solution for my underpowered 304, I have been in search of an auxiliary transmission. I found what I thought I needed which was a 3 speed Under-direct-over drive; the placard on the dash indicated the gears and shift pattern. I thought that they were all the same until yesterday when I found a truck with a 4 speed auxiliary transmission, which was identified as a straight H shift pattern placard, no under-direct-over placard. It is coupled behined a 392 with a LARGE 5 speed main trans (I think I have a T-21? small 5 speed behind a 304) The aux trans behind the 392 is much larger than the 3 speed aux. If it is direct drive in 4th then it won't help me. Does anyone know if they were an overdrive in 4th or direct? Is there a site or person where I can get some technicial information, I am looking for anything I can find.

Thanks,

Jeremy

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Cooter

You just asked a big ole question,that has some long winded

answers.

Brownies come in different ratios,number of speeds,and type.

All 4 speeds are deep under,under, direct,and over. Some are

progressive and the deep under can be shifted on the go and

used to split up to 4th gear on a 5th direct or 4 speed main box.

Some have a double over drive.

The ratio of the brownie needs to match up to the main box and

rear end ratios,engine power,and rpm,or you will have gaps and

worthless gears that are too close to serve a purpose.

The brownie has to be mounted right or it will viberate and cause

all kinds of problems. It has to be centered and the driveline angle

has to be right.

The gear drag can take 30 HP to pull at highway speed. With a

small engine,you will lose power on the top end from gear drag.

Unless you have lots of HP or are running all down hill a double

over drive is worthless.

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I agree with sawmill about the aux. transmission. It has it's place and purpose but maybe not in your situation. I feel your time and money to stick one in might be wasted. I hate to discourage anyone because you probably already know what your going to do anyway.

One final idea that would be fairly easy would be to pull your axles and take your third member out of the jug and replace it with one that has a 2-speed. Call around with your axle tag to salvage yards even if you find one out of state all your after is a 2-speed third member , not the whole rear axle.

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Cooter

HYTRAN is right as rain for your situation.

Around here you can buy the complete 2 speed rear end

for $50.00 and in some cases a complete running 1600 Loadstar.

I know where there is several that can be had for driving them

away. A friend got a slick 1700 ,5 speed,2 speed ,345,and factory

tag with almost new tires all the way around for $250.00.

The old truck runs good too. No one uses them here anymore.

All the older farmers and ranchers have retired or quit. The

ones that are left all use class 8 diesels.

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I am looking to replace the 304 with a powerstroke and 5 speed out of a pickup. I found a 2 speed axle but it still has gas gears in it, so I thought even with the overdrive in the powerstroke transmission still wouldn't be enough to lower the crusing engine RPM........that's where I came up with the aux trans. I would use only a 2 speed rear if I could find one with gears suitable for diesels. Dose anone know what gearing I could use and does anyone know where I could find them? It has 8.25 - 20's and I am looking to cruise 65 @ 22-2400. I THINK that it has 6.33 gears in it now, so 50 @ 4500 is all it will do. Let me know what people think.

Thanks,

Jeremy

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Cooter---

Would be my thinking that simplest and most economical solution for you would be to swap out to a rear end from a diesel truck that already has an appropriate "diesel gear ratio". Maybe looking for something out of a diesel S series (80's model IH)----which replaced the Loadstar. My neighbor has a S-1654 (?) with the small V-8 diesel in it (8.25 tires and a 5 speed). I will try to check and see what rear axle ratio its set up with (and he definitely needs a 2 speed).

I have done alot of calculating on rear end ratios in thinking about improving mileage on a F-700 with a 429 factory propane engine. Already got a 5 speed with 2 speed rear axle (with low ratio)----plenty of power, just burns the **** out of gas. Bottom line is how much are you going to run it------to justify the expense and work involved in changing everything out.

Based on your post of running 50 @ 4500 rpm with the 8.25 x 20s and 6.33 gears---------and looking at desired diesel rpms of 22---2400 (which is 1/2 of your current "gas" 4500 rpm)-----you would need to get up to something in the 3.16-1 ratio just to run 50 @ 2400. I don't have any knowledge as to what ratios are offered------but do see alot of the smaller roll back wrecker trucks roaming around with the smaller diameter tire sizes----so something must be available. Course moving up to a larger tire size would help-----but that's expensive too.

I've got an old '63 1600 with the 304 and 4 speed with 2 speed rear axle. The 2 speed axle (with proper ratios) will allow the 304 to move alot of load----but probably never have the fuel economy that a diesel would have.

You might want to check in over at: www.oldihc.org

That's an old IH truck site that has some good information on it. Check under Truck Talk and then under Loadstar category. Hopefully you can catch up with D Phariss-----he is very knowledgable along these lines. There was some discussion along these lines a year or so ago over there----there doesn't seem to be alot of activity, so you might want to scan back through some of the older posts (seems like some of those posts were centered around overdrive transmissions)----plus I had a post or so asking questions along these lines.

My head is sorta foggy right now-----when I am thinking better, will try to dig some of this info out for you.

Saw a picture of your 1600 with the tractor on its back in one of your posts-----that's a good looking truck. Good luck.

Delta Dirt

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More info for Cooter---

I checked the tag on the rear end of the neighbor's S1600 (1654 on door ID plate----1986 year model). Rear end ratio is 4.78-1-------single speed. Engine is 6.9 diesel with 5 speed transmission. Rear end is square tubing design.

I drove this truck once with a light load-----seems like it topped out @ 58--60 mph, but seemed real sluggish in getting to top speed. The old V-8 304 with the 4 speed and 2 speed rear end would have easily out performed it.

Also found a site that I had saved as a favorite for calculating ratios, tire size, speed and engine rpms----but it doesn't come up when clicked on here on my computer. Has in the past-----and is real helpful. I have seen other similar sites----but didn't save them. If you can't pull this site up----try Google for truck rear end ratios, speed and tire sizes, etc. There are some other sites out there----I just don't remember exactly where they are.

Try this site: www.Randy's ring and pinion.com

(or possibly some variances of the above----that's how its listed on my favorite list)

Don't cut the 304 short----put you a higher ratio 2 speed in behind the 304-----get a little more road speed, and get used to $3 gas (uuuggh)---------and you should be a happy camper versus what all would be involved in switching over to the diesel. And----maybe keep looking around for a good buy on a factory diesel that fits your needs.

Good luck again-----keep us posted---and say hello to Daisy Mae!! B)

Delta Dirt

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